[thirdparty/squid.git] / helpers / external_acl / LDAP_group / ext_ldap_group_acl.cc

/*
 * Copyright (C) 1996-2015 The Squid Software Foundation and contributors
 *
 * Squid software is distributed under GPLv2+ license and includes
 * contributions from numerous individuals and organizations.
 * Please see the COPYING and CONTRIBUTORS files for details.
 */

/*
 * ext_ldap_group_acl: lookup group membership in LDAP
 *
 * Version 2.17
 *
 * (C)2002,2003 MARA Systems AB
 *
 * License: squid_ldap_group is free software; you can redistribute it
 * and/or modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2,
 * or (at your option) any later version.
 *
 * Authors:
 *  Flavio Pescuma <flavio@marasystems.com>
 *  Henrik Nordstrom <hno@marasystems.com>
 *  MARA Systems AB, Sweden <http://www.marasystems.com>
 *
 * With contributions from others mentioned in the ChangeLog file
 *
 * In part based on squid_ldap_auth by Glen Newton and Henrik Nordstrom.
 *
 * Latest version of this program can always be found from MARA Systems
 * at http://marasystems.com/download/LDAP_Group/
 *
 * Dependencies: You need to get the OpenLDAP libraries
 * from http://www.openldap.org or use another compatible
 * LDAP C-API library.
 *
 * If you want to make a TLS enabled connection you will also need the
 * OpenSSL libraries linked into openldap. See http://www.openssl.org/
 */
#include "squid.h"
#include "helpers/defines.h"
#include "rfc1738.h"
#include "util.h"

#define LDAP_DEPRECATED 1

#include <algorithm>
#include <cctype>
#include <cstring>
#include <iomanip>
#include <memory>
#include <sstream>

#if _SQUID_WINDOWS_ && !_SQUID_CYGWIN_

#define snprintf _snprintf
#include <windows.h>
#include <winldap.h>
#ifndef LDAPAPI
#define LDAPAPI __cdecl
#endif
#ifdef LDAP_VERSION3
#ifndef LDAP_OPT_X_TLS
#define LDAP_OPT_X_TLS 0x6000
#endif
/* Some tricks to allow dynamic bind with ldap_start_tls_s entry point at
 * run time.
 */
#undef ldap_start_tls_s
#if LDAP_UNICODE
#define LDAP_START_TLS_S "ldap_start_tls_sW"
typedef WINLDAPAPI ULONG(LDAPAPI * PFldap_start_tls_s) (IN PLDAP, OUT PULONG, OUT LDAPMessage **, IN PLDAPControlW *, IN PLDAPControlW *);
#else
#define LDAP_START_TLS_S "ldap_start_tls_sA"
typedef WINLDAPAPI ULONG(LDAPAPI * PFldap_start_tls_s) (IN PLDAP, OUT PULONG, OUT LDAPMessage **, IN PLDAPControlA *, IN PLDAPControlA *);
#endif /* LDAP_UNICODE */
PFldap_start_tls_s Win32_ldap_start_tls_s;
#define ldap_start_tls_s(l,s,c) Win32_ldap_start_tls_s(l,NULL,NULL,s,c)
#endif /* LDAP_VERSION3 */

#else

#if HAVE_LBER_H
#include <lber.h>
#endif
#if HAVE_LDAP_H
#include <ldap.h>
#endif

#endif

#define PROGRAM_NAME "ext_ldap_group_acl"
#define PROGRAM_VERSION "2.18"

/* Globals */

static const char *basedn = NULL;
static const char *searchfilter = NULL;
static const char *userbasedn = NULL;
static const char *userdnattr = NULL;
static const char *usersearchfilter = NULL;
static const char *binddn = NULL;
static const char *bindpasswd = NULL;
static int searchscope = LDAP_SCOPE_SUBTREE;
static int persistent = 0;
static int noreferrals = 0;
static int aliasderef = LDAP_DEREF_NEVER;
#if defined(NETSCAPE_SSL)
static char *sslpath = NULL;
static int sslinit = 0;
#endif
static int connect_timeout = 0;
static int timelimit = LDAP_NO_LIMIT;

#ifdef LDAP_VERSION3
/* Added for TLS support and version 3 */
static int use_tls = 0;
static int version = -1;
#endif

static int searchLDAP(LDAP * ld, char *group, char *user, char *extension_dn);

static int readSecret(const char *filename);

/* Yuck.. we need to glue to different versions of the API */

#ifndef LDAP_NO_ATTRS
#define LDAP_NO_ATTRS "1.1"
#endif

#if defined(LDAP_API_VERSION) && LDAP_API_VERSION > 1823
static int
squid_ldap_errno(LDAP * ld)
{
    int err = 0;
    ldap_get_option(ld, LDAP_OPT_ERROR_NUMBER, &err);
    return err;
}
static void
squid_ldap_set_aliasderef(LDAP * ld, int deref)
{
    ldap_set_option(ld, LDAP_OPT_DEREF, &deref);
}
static void
squid_ldap_set_referrals(LDAP * ld, int referrals)
{
    int *value = static_cast<int*>(referrals ? LDAP_OPT_ON :LDAP_OPT_OFF);
    ldap_set_option(ld, LDAP_OPT_REFERRALS, value);
}
static void
squid_ldap_set_timelimit(LDAP * ld, int aTimeLimit)
{
    ldap_set_option(ld, LDAP_OPT_TIMELIMIT, &aTimeLimit);
}
static void
squid_ldap_set_connect_timeout(LDAP * ld, int aTimeLimit)
{
#if defined(LDAP_OPT_NETWORK_TIMEOUT)
    struct timeval tv;
    tv.tv_sec = aTimeLimit;
    tv.tv_usec = 0;
    ldap_set_option(ld, LDAP_OPT_NETWORK_TIMEOUT, &tv);
#elif defined(LDAP_X_OPT_CONNECT_TIMEOUT)
    aTimeLimit *= 1000;
    ldap_set_option(ld, LDAP_X_OPT_CONNECT_TIMEOUT, &aTimeLimit);
#endif
}
static void
squid_ldap_memfree(char *p)
{
    ldap_memfree(p);
}

#else
static int
squid_ldap_errno(LDAP * ld)
{
    return ld->ld_errno;
}
static void
squid_ldap_set_aliasderef(LDAP * ld, int deref)
{
    ld->ld_deref = deref;
}
static void
squid_ldap_set_referrals(LDAP * ld, int referrals)
{
    if (referrals)
        ld->ld_options |= ~LDAP_OPT_REFERRALS;
    else
        ld->ld_options &= ~LDAP_OPT_REFERRALS;
}
static void
squid_ldap_set_timelimit(LDAP * ld, int timelimit)
{
    ld->ld_timelimit = timelimit;
}
static void
squid_ldap_set_connect_timeout(LDAP * ld, int timelimit)
{
    fprintf(stderr, "WARNING: Connect timeouts not supported in your LDAP library\n");
}
static void
squid_ldap_memfree(char *p)
{
    free(p);
}

#endif

#ifdef LDAP_API_FEATURE_X_OPENLDAP
#if LDAP_VENDOR_VERSION > 194
#define HAS_URI_SUPPORT 1
#endif
#endif

int
main(int argc, char **argv)
{
    char buf[HELPER_INPUT_BUFFER];
    char *user, *group, *extension_dn = NULL;
    char *ldapServer = NULL;
    LDAP *ld = NULL;
    int tryagain = 0, rc;
    int port = LDAP_PORT;
    int use_extension_dn = 0;
    int strip_nt_domain = 0;
    int strip_kerberos_realm = 0;

    setbuf(stdout, NULL);

    while (argc > 1 && argv[1][0] == '-') {
        const char *value = "";
        char option = argv[1][1];
        switch (option) {
        case 'P':
        case 'R':
        case 'z':
        case 'Z':
        case 'd':
        case 'g':
        case 'S':
        case 'K':
            break;
        default:
            if (strlen(argv[1]) > 2) {
                value = argv[1] + 2;
            } else if (argc > 2) {
                value = argv[2];
                ++argv;
                --argc;
            } else
                value = "";
            break;
        }
        ++argv;
        --argc;
        switch (option) {
        case 'H':
#if !HAS_URI_SUPPORT
            fprintf(stderr, "FATAL: Your LDAP library does not have URI support\n");
            exit(1);
#endif
        /* Fall thru to -h */
        case 'h':
            if (ldapServer) {
                int len = strlen(ldapServer) + 1 + strlen(value) + 1;
                char *newhost = static_cast<char*>(xmalloc(len));
                snprintf(newhost, len, "%s %s", ldapServer, value);
                free(ldapServer);
                ldapServer = newhost;
            } else {
                ldapServer = xstrdup(value);
            }
            break;
        case 'b':
            basedn = value;
            break;
        case 'f':
            searchfilter = value;
            break;
        case 'B':
            userbasedn = value;
            break;
        case 'F':
            usersearchfilter = value;
            break;
        case 'u':
            userdnattr = value;
            break;
        case 's':
            if (strcmp(value, "base") == 0)
                searchscope = LDAP_SCOPE_BASE;
            else if (strcmp(value, "one") == 0)
                searchscope = LDAP_SCOPE_ONELEVEL;
            else if (strcmp(value, "sub") == 0)
                searchscope = LDAP_SCOPE_SUBTREE;
            else {
                fprintf(stderr, PROGRAM_NAME ": FATAL: Unknown search scope '%s'\n", value);
                exit(1);
            }
            break;
        case 'E':
#if defined(NETSCAPE_SSL)
            sslpath = value;
            if (port == LDAP_PORT)
                port = LDAPS_PORT;
#else
            fprintf(stderr, PROGRAM_NAME ": FATAL: -E unsupported with this LDAP library\n");
            exit(1);
#endif
            break;
        case 'c':
            connect_timeout = atoi(value);
            break;
        case 't':
            timelimit = atoi(value);
            break;
        case 'a':
            if (strcmp(value, "never") == 0)
                aliasderef = LDAP_DEREF_NEVER;
            else if (strcmp(value, "always") == 0)
                aliasderef = LDAP_DEREF_ALWAYS;
            else if (strcmp(value, "search") == 0)
                aliasderef = LDAP_DEREF_SEARCHING;
            else if (strcmp(value, "find") == 0)
                aliasderef = LDAP_DEREF_FINDING;
            else {
                fprintf(stderr, PROGRAM_NAME ": FATAL: Unknown alias dereference method '%s'\n", value);
                exit(1);
            }
            break;
        case 'D':
            binddn = value;
            break;
        case 'w':
            bindpasswd = value;
            break;
        case 'W':
            readSecret(value);
            break;
        case 'P':
            persistent = !persistent;
            break;
        case 'p':
            port = atoi(value);
            break;
        case 'R':
            noreferrals = !noreferrals;
            break;
#ifdef LDAP_VERSION3
        case 'v':
            switch (atoi(value)) {
            case 2:
                version = LDAP_VERSION2;
                break;
            case 3:
                version = LDAP_VERSION3;
                break;
            default:
                fprintf(stderr, "FATAL: Protocol version should be 2 or 3\n");
                exit(1);
            }
            break;
        case 'Z':
            if (version == LDAP_VERSION2) {
                fprintf(stderr, "FATAL: TLS (-Z) is incompatible with version %d\n",
                        version);
                exit(1);
            }
            version = LDAP_VERSION3;
            use_tls = 1;
            break;
#endif
        case 'd':
            debug_enabled = 1;
            break;
        case 'g':
            use_extension_dn = 1;
            break;
        case 'S':
            strip_nt_domain = 1;
            break;
        case 'K':
            strip_kerberos_realm = 1;
            break;
        default:
            fprintf(stderr, PROGRAM_NAME ": FATAL: Unknown command line option '%c'\n", option);
            exit(1);
        }
    }

    while (argc > 1) {
        char *value = argv[1];
        if (ldapServer) {
            int len = strlen(ldapServer) + 1 + strlen(value) + 1;
            char *newhost = static_cast<char*>(xmalloc(len));
            snprintf(newhost, len, "%s %s", ldapServer, value);
            free(ldapServer);
            ldapServer = newhost;
        } else {
            ldapServer = xstrdup(value);
        }
        --argc;
        ++argv;
    }

    if (!ldapServer)
        ldapServer = (char *) "localhost";

    if (!basedn || !searchfilter) {
        fprintf(stderr, "\n" PROGRAM_NAME " version " PROGRAM_VERSION "\n\n");
        fprintf(stderr, "Usage: " PROGRAM_NAME " -b basedn -f filter [options] ldap_server_name\n\n");
        fprintf(stderr, "\t-b basedn (REQUIRED)\tbase dn under where to search for groups\n");
        fprintf(stderr, "\t-f filter (REQUIRED)\tgroup search filter pattern. %%u = user,\n\t\t\t\t%%v = group\n");
        fprintf(stderr, "\t-B basedn (REQUIRED)\tbase dn under where to search for users\n");
        fprintf(stderr, "\t-F filter (REQUIRED)\tuser search filter pattern. %%s = login\n");
        fprintf(stderr, "\t-s base|one|sub\t\tsearch scope\n");
        fprintf(stderr, "\t-D binddn\t\tDN to bind as to perform searches\n");
        fprintf(stderr, "\t-w bindpasswd\t\tpassword for binddn\n");
        fprintf(stderr, "\t-W secretfile\t\tread password for binddn from file secretfile\n");
#if HAS_URI_SUPPORT
        fprintf(stderr, "\t-H URI\t\t\tLDAPURI (defaults to ldap://localhost)\n");
#endif
        fprintf(stderr, "\t-h server\t\tLDAP server (defaults to localhost)\n");
        fprintf(stderr, "\t-p port\t\t\tLDAP server port (defaults to %d)\n", LDAP_PORT);
        fprintf(stderr, "\t-P\t\t\tpersistent LDAP connection\n");
#if defined(NETSCAPE_SSL)
        fprintf(stderr, "\t-E sslcertpath\t\tenable LDAP over SSL\n");
#endif
        fprintf(stderr, "\t-c timeout\t\tconnect timeout\n");
        fprintf(stderr, "\t-t timelimit\t\tsearch time limit\n");
        fprintf(stderr, "\t-R\t\t\tdo not follow referrals\n");
        fprintf(stderr, "\t-a never|always|search|find\n\t\t\t\twhen to dereference aliases\n");
#ifdef LDAP_VERSION3
        fprintf(stderr, "\t-v 2|3\t\t\tLDAP version\n");
        fprintf(stderr, "\t-Z\t\t\tTLS encrypt the LDAP connection, requires\n\t\t\t\tLDAP version 3\n");
#endif
        fprintf(stderr, "\t-g\t\t\tfirst query parameter is base DN extension\n\t\t\t\tfor this query\n");
        fprintf(stderr, "\t-S\t\t\tStrip NT domain from usernames\n");
        fprintf(stderr, "\t-K\t\t\tStrip Kerberos realm from usernames\n");
        fprintf(stderr, "\t-d\t\t\tenable debug mode\n");
        fprintf(stderr, "\n");
        fprintf(stderr, "\tIf you need to bind as a user to perform searches then use the\n\t-D binddn -w bindpasswd or -D binddn -W secretfile options\n\n");
        exit(1);
    }
    /* On Windows ldap_start_tls_s is available starting from Windows XP,
     * so we need to bind at run-time with the function entry point
     */
#if _SQUID_WINDOWS_
    if (use_tls) {

        HMODULE WLDAP32Handle;

        WLDAP32Handle = GetModuleHandle("wldap32");
        if ((Win32_ldap_start_tls_s = (PFldap_start_tls_s) GetProcAddress(WLDAP32Handle, LDAP_START_TLS_S)) == NULL) {
            fprintf(stderr, PROGRAM_NAME ": FATAL: TLS (-Z) not supported on this platform.\n");
            exit(1);
        }
    }
#endif

    while (fgets(buf, HELPER_INPUT_BUFFER, stdin) != NULL) {
        int found = 0;
        if (!strchr(buf, '\n')) {
            /* too large message received.. skip and deny */
            fprintf(stderr, "%s: ERROR: Input Too large: %s\n", argv[0], buf);
            while (fgets(buf, sizeof(buf), stdin)) {
                fprintf(stderr, "%s: ERROR: Input Too large..: %s\n", argv[0], buf);
                if (strchr(buf, '\n') != NULL)
                    break;
            }
            SEND_ERR("");
            continue;
        }
        user = strtok(buf, " \n");
        if (!user) {
            debug("%s: Invalid request: No Username given\n", argv[0]);
            SEND_ERR("Invalid request. No Username");
            continue;
        }
        rfc1738_unescape(user);
        if (strip_nt_domain) {
            char *u = strrchr(user, '\\');
            if (!u)
                u = strrchr(user, '/');
            if (!u)
                u = strrchr(user, '+');
            if (u && u[1])
                user = u + 1;
        }
        if (strip_kerberos_realm) {
            char *u = strchr(user, '@');
            if (u != NULL) {
                *u = '\0';
            }
        }
        if (use_extension_dn) {
            extension_dn = strtok(NULL, " \n");
            if (!extension_dn) {
                debug("%s: Invalid request: Extension DN configured, but none sent.\n", argv[0]);
                SEND_ERR("Invalid Request. Extension DN required.");
                continue;
            }
            rfc1738_unescape(extension_dn);
        }
        while (!found && user && (group = strtok(NULL, " \n")) != NULL) {
            rfc1738_unescape(group);

recover:
            if (ld == NULL) {
#if HAS_URI_SUPPORT
                if (strstr(ldapServer, "://") != NULL) {
                    rc = ldap_initialize(&ld, ldapServer);
                    if (rc != LDAP_SUCCESS) {
                        fprintf(stderr, "%s: ERROR: Unable to connect to LDAPURI:%s\n", argv[0], ldapServer);
                        break;
                    }
                } else
#endif
#if NETSCAPE_SSL
                    if (sslpath) {
                        if (!sslinit && (ldapssl_client_init(sslpath, NULL) != LDAP_SUCCESS)) {
                            fprintf(stderr, "FATAL: Unable to initialise SSL with cert path %s\n", sslpath);
                            exit(1);
                        } else {
                            ++sslinit;
                        }
                        if ((ld = ldapssl_init(ldapServer, port, 1)) == NULL) {
                            fprintf(stderr, "FATAL: Unable to connect to SSL LDAP server: %s port:%d\n",
                                    ldapServer, port);
                            exit(1);
                        }
                    } else
#endif
                        if ((ld = ldap_init(ldapServer, port)) == NULL) {
                            fprintf(stderr, "ERROR: Unable to connect to LDAP server:%s port:%d\n", ldapServer, port);
                            break;
                        }
                if (connect_timeout)
                    squid_ldap_set_connect_timeout(ld, connect_timeout);

#ifdef LDAP_VERSION3
                if (version == -1) {
                    version = LDAP_VERSION3;
                }
                if (ldap_set_option(ld, LDAP_OPT_PROTOCOL_VERSION, &version) != LDAP_SUCCESS) {
                    fprintf(stderr, "ERROR: Could not set LDAP_OPT_PROTOCOL_VERSION %d\n",
                            version);
                    ldap_unbind(ld);
                    ld = NULL;
                    break;
                }
                if (use_tls) {
#ifdef LDAP_OPT_X_TLS
                    if (version != LDAP_VERSION3) {
                        fprintf(stderr, "FATAL: TLS requires LDAP version 3\n");
                        exit(1);
                    } else if (ldap_start_tls_s(ld, NULL, NULL) != LDAP_SUCCESS) {
                        fprintf(stderr, "ERROR: Could not Activate TLS connection\n");
                        ldap_unbind(ld);
                        ld = NULL;
                        break;
                    }
#else
                    fprintf(stderr, "FATAL: TLS not supported with your LDAP library\n");
                    exit(1);
#endif
                }
#endif
                squid_ldap_set_timelimit(ld, timelimit);
                squid_ldap_set_referrals(ld, !noreferrals);
                squid_ldap_set_aliasderef(ld, aliasderef);
                if (binddn && bindpasswd && *binddn && *bindpasswd) {
                    rc = ldap_simple_bind_s(ld, binddn, bindpasswd);
                    if (rc != LDAP_SUCCESS) {
                        fprintf(stderr, PROGRAM_NAME ": WARNING: could not bind to binddn '%s'\n", ldap_err2string(rc));
                        ldap_unbind(ld);
                        ld = NULL;
                        break;
                    }
                }
                debug("Connected OK\n");
            }
            if (searchLDAP(ld, group, user, extension_dn) == 0) {
                found = 1;
                break;
            } else {
                if (tryagain) {
                    tryagain = 0;
                    ldap_unbind(ld);
                    ld = NULL;
                    goto recover;
                }
            }
        }
        if (found)
            SEND_OK("");
        else {
            SEND_ERR("");
        }

        if (ld != NULL) {
            if (!persistent || (squid_ldap_errno(ld) != LDAP_SUCCESS && squid_ldap_errno(ld) != LDAP_INVALID_CREDENTIALS)) {
                ldap_unbind(ld);
                ld = NULL;
            } else {
                tryagain = 1;
            }
        }
    }
    if (ld)
        ldap_unbind(ld);
    return 0;
}

static std::string
ldap_escape_value(const std::string &src)
{
    std::stringstream str;
    for (const auto &c : src) {
        switch (c) {
        case '*':
        case '(':
        case ')':
        case '\\':
            str << '\\' << std::setfill('0') << std::setw(2) << std::hex << static_cast<int>(c);
            break;
        default:
            str << c;
        }
    }
    return str.str();
}

static bool
build_filter(std::string &filter, const char *templ, const char *user, const char *group)
{
    std::stringstream str;
    while (*templ) {
        switch (*templ) {
        case '%':
            ++templ;
            switch (*templ) {
            case 'u':
            case 'v':
                ++templ;
                str << ldap_escape_value(user);
                break;
            case 'g':
            case 'a':
                ++templ;
                str << ldap_escape_value(group);
                break;
            default:
                fprintf(stderr, "ERROR: Unknown filter template string %%%c\n", *templ);
                filter = str.str();
                return false;
            }
            break;
        case '\\':
            ++templ;
            if (*templ) {
                str << *templ;
                ++templ;
            }
            break;
        default:
            str << *templ;
            ++templ;
            break;
        }
    }
    filter = str.str();
    return true;
}

static std::string
build_searchbase(const char *extension_dn, const char *base_dn)
{
    std::stringstream searchBaseStream;
    if (extension_dn && *extension_dn)
        searchBaseStream << extension_dn << ",";
    searchBaseStream << basedn;
    return searchBaseStream.str();
}

static bool ldap_search_ok(const int result)
{
    if (result == LDAP_SUCCESS)
        return true;
    if (noreferrals && result == LDAP_PARTIAL_RESULTS) {
        /* Everything is fine. This is expected when referrals
         * are disabled.
         */
        return true;
    }
    std::cerr << PROGRAM_NAME << ": WARNING: LDAP search error '" <<
              ldap_err2string(result) << "'" << std::endl;
#if defined(NETSCAPE_SSL)
    if (sslpath && ((result == LDAP_SERVER_DOWN) || (result == LDAP_CONNECT_ERROR))) {
        int sslerr = PORT_GetError();
        std::cerr << PROGRAM_NAME << ": WARNING: SSL error " << sslerr << " (" <<
                  ldapssl_err2string(sslerr) << ")" << std::endl;
    }
#endif
    return false;
}

typedef const std::unique_ptr<LDAPMessage, decltype(&ldap_msgfree)> LdapResult;

static int
searchLDAPGroup(LDAP * ld, const char *group, const char *member, const char *extension_dn)
{
    std::string filter;
    LDAPMessage *res = NULL;
    int rc;
    char *searchattr[] = {(char *) LDAP_NO_ATTRS, NULL};

    const std::string searchbase = build_searchbase(extension_dn, basedn);
    if (!build_filter(filter, searchfilter, member, group)) {
        std::cerr << PROGRAM_NAME  << ": ERROR: Failed to construct LDAP search filter. filter=\"" <<
                  filter.c_str() << "\", user=\"" << member << "\", group=\"" << group << "\"" << std::endl;
        return 1;
    }
    debug("group filter '%s', searchbase '%s'\n", filter.c_str(), searchbase.c_str());

    rc = ldap_search_s(ld, searchbase.c_str(), searchscope, filter.c_str(), searchattr, 1, &res);
    LdapResult ldapRes(res, ldap_msgfree);
    if (!ldap_search_ok(rc))
        return 1;

    return ldap_first_entry(ld, ldapRes.get()) ? 0 : 1;
}

static void
formatWithString(std::string &formatted, const std::string &value)
{
    size_t start_pos = 0;
    while ((start_pos = formatted.find("%s", start_pos)) != std::string::npos) {
        formatted.replace(start_pos, 2, value);
        start_pos += 2;
    }
}

static int
searchLDAP(LDAP * ld, char *group, char *login, char *extension_dn)
{

    const char *current_userdn = userbasedn ? userbasedn : basedn;
    if (usersearchfilter) {
        LDAPMessage *res = NULL;
        LDAPMessage *entry;
        int rc;
        char *userdn;
        char *searchattr[] = {(char *) LDAP_NO_ATTRS, NULL};
        const std::string searchbase = build_searchbase(extension_dn, current_userdn);
        std::string filter(usersearchfilter);
        const std::string escaped_login = ldap_escape_value(login);
        formatWithString(filter, escaped_login);

        debug("user filter '%s', searchbase '%s'\n", filter.c_str(), searchbase.c_str());
        rc = ldap_search_s(ld, searchbase.c_str(), searchscope, filter.c_str(), searchattr, 1, &res);
        LdapResult ldapRes(res, ldap_msgfree);
        if (!ldap_search_ok(rc))
            return 1;
        entry = ldap_first_entry(ld, ldapRes.get());
        if (!entry) {
            std::cerr << PROGRAM_NAME << ": WARNING: User '" << login <<
                      " not found in '" << searchbase.c_str() << "'" << std::endl;
            return 1;
        }
        userdn = ldap_get_dn(ld, entry);
        rc = searchLDAPGroup(ld, group, userdn, extension_dn);
        squid_ldap_memfree(userdn);
        return rc;
    } else if (userdnattr) {
        std::stringstream str;
        str << userdnattr << "=" << login << ", ";
        if (extension_dn && *extension_dn)
            str << extension_dn << ", ";
        str << current_userdn;
        return searchLDAPGroup(ld, group, str.str().c_str(), extension_dn);
    } else {
        return searchLDAPGroup(ld, group, login, extension_dn);
    }
}

int
readSecret(const char *filename)
{
    char buf[BUFSIZ];
    char *e = 0;
    FILE *f;

    if (!(f = fopen(filename, "r"))) {
        fprintf(stderr, PROGRAM_NAME ": ERROR: Can not read secret file %s\n", filename);
        return 1;
    }
    if (!fgets(buf, sizeof(buf) - 1, f)) {
        fprintf(stderr, PROGRAM_NAME ": ERROR: Secret file %s is empty\n", filename);
        fclose(f);
        return 1;
    }
    /* strip whitespaces on end */
    if ((e = strrchr(buf, '\n')))
        *e = 0;
    if ((e = strrchr(buf, '\r')))
        *e = 0;

    bindpasswd = xstrdup(buf);
    if (!bindpasswd) {
        fprintf(stderr, PROGRAM_NAME ": ERROR: can not allocate memory\n");
    }
    fclose(f);

    return 0;
}